i was wondering if there will a release of a texture pack for mappers?
i would like to work on some NS2 map but i don't have suitable textures

Keep in mind that NS2 is on its own engine and will be using its own mapping utilities. Any work that you do in hammer will be useless unless UW is kind enough to make hammer compatible with their mapping program.

For know, just keep running some concepts through your head. That will give you a pretty nice idea of how exactly your map will look and work.

As with the original NS, the developers will release a stripped down version of the game (textures, props and really basic gameplay elements), as soon as they possibly can. And since NS2 requires it's own set of tools, I think these will be included as well. (map editor, texture viewer, stuff like that). This release is commonly referred to as the NS2TR (TR for tech release).

(If you are bored and curious (very dangerous combination...) I suggest that you track down the original NSTR. It will give you some idea of what to expect, and it features a skulk model well worth a race).